Osteoarthritis or osteoarthrosis is a degenerative joint disease which commonly affects both axial and peripheral diarthrodial joints in humans. Moreover, since the incidence of this disease increases steadily with age, it is an almost universal occurrence in the elderly.
Pathological characteristics of osteoarthritis include progressive deterioration and loss of articular cartilage from the surfaces of joints, as well as reactive changes at the joint margins and the underlying bone. Manifestations of the disease that are treatable are joint pain, stiffness and limitation of motion. Synovitis or joint inflammation is also a common secondary manifestation of the disease that is also treatable. Although, as aforementioned, high incidence of the disease occurs in the elderly, the treatment is highly individualized and may include (a) prescription of a pharmacological agent, (b) a surgical procedure, or (c) a physical modality.
Conventionally, patients exhibiting symptomatic osteoarthritis are initially treated by their physician by the administration of a nonsteroidal anti-inflammatory drug (NSAID). As indicated by U.S. Pat. No. 4,997,850 issued to Kimura et al and U.S. Pat. No. 4,944,949 issued to Story et al, many such nonsteroidal anti-inflammatory drugs are known and are frequently effective in reducing the symptoms of osteoarthritis. That is to say, they have demonstrated value in helping &:o relieve pain, improve activity levels, and in some cases improve function in osteoarthritic patients. Many members of this class of drugs have been approved by the U.S. Food and Drug Administration for the treatment of osteoarthritis.
None of these drugs, however, have been proven in carefully controlled clinical trials to reverse the long term natural history of this degenerative joint disease. Moreover, while many of these drugs have demonstrated effectiveness in treating the symptoms of osteoarthritis, they also have been associated with significant toxicities and other risks, such as deleterious effects on cartilage when used over prolonged periods of time. In March of 1989, for example, the U.S. Food and Drug Administration moved to warn both doctors and the public about the use of such drugs which were said to have become the No. 1 cause of complications among all prescription drugs. Moreover, in addition to being very expensive the toxicities of such drugs limit their usefulness, particularly in elderly patients.
In this regard, the above noted patent to Story et al recognizes that nonsteroidal anti-inflammatory drugs are the drugs of choice for various forms of inflammatory arthropathy including osteoarthritis, but that their prostaglandin inhibiting property responsible for their effectiveness may also be responsible for reducing the protective effects of prostaglandin on gastrointestinal mucosa. Story et al indicate that conventional enteric coatings applied over such drugs have not been fully effective and thereafter it is said that they have discovered that the use of micelles enables a particularly appropriate form of such nonsteroidal anti-inflammatory drugs to be achieved.
A second form of treating osteoarthritis involves surgery including non-replacement as well as joint replacement procedures. The latter procedures are usually offered only after non-operative as well as non-replacement surgical measures have been exhausted. Such surgical procedures as currently used vary greatly as to complexity, cost, success rate and risk, and in many respects are not alternative therapies vis-a-vis pharmacological agents and physical modalities.
The third major known form of treatment for osteoarthritis; namely, physical modalities, are useful in reducing pain and/or restoring function, particularly in patients for whom pharmacological agents have either been minimally effective or have been poorly tolerated. Although this general form of treatment would include simple bed rest, traction and heat treatment, among other things, the most widely studied is that of modifying pain perception via electrical nerve stimulation using noninvasive transcutaneous electrical nerve stimulators (TENS).
Pain modulation or control of pain by electrical stimulation is conventionally accomplished in three ways; namely, (1) sensory level stimulation, (2) motor level stimulation, and (3) noxious-level stimulation. As to the first, which is the most widely recognized and studied, electrical stimulation is delivered at or above a level felt by the patient but below motor level threshold. Such sensory level stimulation is generally obtained with low level pulses in the frequency range of 50-100 hertz with pulse widths in the range of 2-50 microseconds. Such sensory level stimulation is for the purpose of stimulating or activating only the largest diameter superficial nerve and is generally effective in the relief of acute pain problems.
Motor level stimulation, which by definition produces muscle contraction, is most often used clinically with chronic pain patients. Such motor level stimulation is generally accomplished in a frequency range of 2-4 hertz with pulse widths greater than 150 microseconds and intensities high enough to produce a strong visible muscle contraction.
Noxious level stimulation will produce a painful stimulus at the pain site or a site remote from the pain site and is generally accomplished in the frequency range of 1-5 hertz or greater than 100 hertz with long pulse durations of up to 1 second and at intensities which produce painful sensory stimulation with or without muscle contraction. Such stimulation may cause a quick onset of pain relief identified as "hyperstimulation analgesia".
Substantially all commercially available transcutaneous electrical nerve stimulators (TENS) can produce stimulation at each of the aforementioned levels, and several are marketed with instructions for using the device at each of the noted levels by way of adjustment of current, voltage or other delivery characteristics.
Exemplary prior art transcutaneous electrical nerve stimulators may be found in U.S. Pat. No. 3,881,494 to Paul et al and U.S. Pat. No. 3,902,502 to Liss. The Paul et al device is said to be provide temporary pain relief to arthritic patients when the level of current used in the treatment is the maximum level the patient can comfortably endure. Liss, on the other hand, discloses a device for producing a one-way low current at a frequency of 20 kilocycles to 1 megacycle with an on duty cycle of 75% modulated at 10-40 hertz. It is said that the apparatus with the electrodes properly positioned along nerves provides a nerve stimulator, which, although battery powered, employs a small current that often requires a viewing of the meter to be sure that treatment is in process. A manual control is provided whereby the patient may reduce the input to tolerable levels until repeated use builds up a conditioning acceptance. It is additionally indicated that the current flow is applied to give a pumping action to the nerve train between the applied contact points, and the impedance of the patient is compensated by the constant current circuit which is automatically readjusted to the needs of the patient.
Most commercially available transcutaneous electrical nerve stimulators are current sourced and have a common goal in addition to pain relief of comfortable treatment so as to reduce apprehension as to the electrical aspect of the treatment. Conventionally, the patient using such devices is instructed to slowly advance the amplitude control until the electrical stimulation is felt with subsequent higher settings used as the patient becomes accustomed to the stimulation. As demonstrated by such devices, electrical stimulation employed in the form of transcutaneous electrical nerve stimulators is a potentially important physical modality for the treatment of pain in a broad variety of medical problems. Although a number of such devices have indications pertaining to effective pain treatment under the broad term of arthritis and a few include osteoarthritic pain, such prior devices have not been carefully clinically studied or consistently employed to directly treat still other important aspects of osteoarthritis, such as joint stiffness, range of motion and function.
Accordingly, it is the primary object of the present invention to employ a method and apparatus having demonstrated statistically significant improvement for all of the primary clinical measures of osteoarthritis. Such measures include independent clinical measures of joint stiffness, range of motion and overall function in addition to reduction in pain. More specifically, I have discovered a method and apparatus for the treatment of the broader aspects that define osteoarthritis by using electrical stimulation at a subsensory level whereby the amplitude of the voltage source signal is first adjusted to provide a slight sensation to the patient and thereafter immediately reduced to a subsensory level for the duration of the treatment. Such treatment has been clinically shown in carefully controlled double-blinded trials to reduce osteoarthritis joint pain, improve the range of joint motion, reduce morning stiffness and improve joint function as judged by the patient, as well as a physicians global evaluation in five medical centers.